Electronic devices such as wireless communications terminals typically include a display and a keypad which function as a user interface. Electronic devices often are used in poorly lit or dark environments, so that it may be desirable to illuminate the displays and keypads thereof. Illuminating such displays and keypads may present technical challenges for wireless communications terminals, and many other types of electronic devices, due to the desirability of decreasing the size and decreasing the power consumption of the wireless communications terminals, while at the same time providing bright, evenly distributed illumination.
Some electronic devices utilize Light Emitting Diodes (LEDs) and a lightguide to provide backlight illumination of displays/keypads. The LEDs emit light into a transparent material lightguide which guides the light until it meets surfaces that are designed to reflect light up through the display/keypad. Some lightguides are made of a dispersing (translucent) material, so that light is more uniformly scattered and emitted through the display/keypad. Unfortunately, lightguides may have low optical efficiency due to the desire to make the lightguide thin and/or the desire to provide holes and/or other deformations therein to accommodate other components of the electronic device. Moreover, since LEDs may send out light in many directions, efficient optical coupling to the lightguide may be difficult. It may also be difficult to obtain evenly distributed light from a lightguide so that about the same luminescence is provided across a coupled display/keypad.
Some electronic devices use electroluminescent panels to provide backlight illumination of displays/keypads. Electroluminescent panels may be formed as thin flexible sheets that may more uniformly illuminate a coupled display/keypad than may be provided by LED and lightguide configurations.